Incandescent lamp.



No. 638,839. Patented Deb. l2, I899. R. A. FESSENDEN.

INCANDESCENT LAMP.

(Application filed Aug. 25, 1899.)

(No Model.)

FIGQI- ilurrnn STATES PATENT Urrrcn. V

REGINALD A. FESSENDEN, OF ALLEGHENY, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TO GRANT MOGARGO, OF PITTSBURG, PENNSYLVANIA.

INCANDESCENT LAMP.

SPECIFICATION forming part of Letters Patent No. 638,839, dated December 12, 1899.

Application filed August 25, 1899. Serial No. 728,421. (No model.)

To aZZ whom it may concern: metal 7, embedded in the pencils. These Be itknown thatLREGINALDAFESSENDEN, pieces of metal are made of such a size that a citizen of the United States, residing at Alletheir outer edges will be flush with the surgheny, in the county of Allegheny and State face of the pencil, and the pitch of the spiral 55 of Pennsylvania,have invented or discovered preferably corresponds with the pitch of the certain new and useful Improvements in 111- threads on the shaft 8. This shaft 8, which candescent Lamps, of which improvements has its ends mounted in bearings 9, secured to the following is a specification. the shell 3, has an internally-threaded car- In an application, Serial No. 726,395, filed rier-block 9 mounted thereon. A block 10, 6o 10 August 7, 1899, I have described and claimed formed of graphite or other conducting macertainimprovements in incandescent lamps terial neutralizable as regards its capability employing pencils which become electric con of conducting electric currents at high temductors only when heated. The invention peratures, is attached to the carrier-block, set forth in said application consists, genen preferably by a spring 11 or by any other I5 ally stated, in providing a path for electric suitable means, whereby the connecting macurrents along the pencil for the purpose of terial may be held in rubbing contact with heating the pencil to a conducting temperathe pencil. The shaft 8 may be rotated so ture. as to cause the block of conducting material The present invention has for its object to traverse the pencil by any suitable means; 20 certain further improvements in the means but as it is preferred to cause the pencil to for forming a path for the electric current rotate during the traverse of the block pinalong the surface of the pencil. ions 12 and 13 are secured, respectively, on

In the accompanying drawings, forming a the shaft 8 and pin I said pinions interpart of this specification, Figure 1 is a s'ecmeshing with a drivingpinion 14, secured on 25 tional elevation of a lamp having my imone end of a shaft 15, which projects through provement applied thereto, and Figs. 2 and a suitable bearing 16 and has a knob 17 se 3 are sectional detail views of parts of the cured to its outer end. As shown in Fig. 3, lamp. the pinion 13 is insulated from the pin 1.

'In the practice of my invention the sup- The carrier-block may be held as against roo porting-pins 1 1 are mounted in suitable tation with the shaft 8 by any suitable bearings 2, preferably formed of insulating means-as, for example, by a rod 18, secured material and secured to the sides of the domeat its ends to the shell 3 and passing loosely shaped shell 3, which has its inner surface through an upward extension of the carrierhighly polished. One of the pins, as 1, problock. 3 5 jects through the case or shell and is so The feed-wires 19 are attached to contactmounted in its hearing as to be capable of plates 20 and 20-, secured toinsulating-blocks longitudinal as well as rotary movement and attached to the shell, and corresponding conislheld in normal position,so as to support one tact-plates 21 21 are attached to the disks 5 end of the pencil 4, by a spring 5, surrounding and 6 on the pins 1 and 1". As the pins 1 and 0 c the pin and hearing at its ends against the 1 are electrically connected to the contactbearing 2, and a disk 6, formed of insulating plates 21 21, the rotation of the pins will commaterial and secured on the pin. The pencil plete the circuit through the pencil. The 4:, which is formed of magnesia, kaolin, or contact-plates 20 20 and 21 21 are so conother material non-conducting when cold,but structed and arranged that the latter can slide 9 5 45 becoming a conductor when heated, is propast the plates 20 20 when the disks 5 and 6 vided at its ends with axial holes or sockets are rotated. for the reception of the ends of the pins 1 By the rotation of the driving-pinion let the and 1. The pins bear at their ends, which block 10, of graphite, will be caused to move are preferably made angular or irregular in along the pencil, which is also rotated, so that I00 50 cross section, against the inner edges of tera spiral band or, if theblock 10 is sufficiently minals formed of a spirally-bent piece of long, a complete coat of graphite will be applied to the pencil. As the edges of the metal terminals 7 are exposed'and flush with the surface of the pencil, a conductor will be formed along the surface of the pencil from terminal to terminal. The passage of the current along the conductor will heat the pencil sufficiently to render it conducting. As soon as the pencil is raised to a high heat the material used to form a conducting-path Will be destroyed or rendered neutral, so that the entire current Will pass through the pencil.

Although it may require several rotations of the shaft 8 to eifecttheend-to-end traverse of the carrier-block, the meeting of the contact-plates Will not close the circuit, as no current can pass until a conducting-path is for-med from terminal to terminal.

It is preferred to place blocks 22, formed of non-conducting material, on the pins 1 and l adjacent to the ends of the pencils, to serve as supports for the blocks 10.

I claim herein as my invention 1. In an incandescent lamp, the combination of a pencil non-conductive at low temperatures, but conductive at high temperatures;

a carrier for a conducting material neutralizable at high temperatures, and means for causing the carrier to move along the pencil, substantially as set forth. 7

2. In an incandescent lamp, the combination of a pencil non-conductive at low temperatures, but conductive at high temperatures; a carrier for a conducting material neutralizable at high temperatures, and means for simultaneously rotating the pencil and shifting the carrier along the pencil, substantially as set forth.

3. In an incandescent lamp, the combination of two rotatable pins adapted to support and rotate a pencil, a threaded shaft, a carrier-block mounted on the shaft and means for simultaneously rotating the shaft and pins, substantially as set forth.

In testimony whereof I have hereunto set my hand.

REGINALD A. FESSENDEN.

Witnesses:

DARWIN S. WoLco'r'r, M. S. MURPHY. 

